1. Field of the Invention
The present invention relates to an information processing apparatus and a communication control method which allow each of multiple logical partitions to communicate with an external entity.
2. Description of the Related Art
A technology is known in which computing resources in a single computer system including a CPU, memory, I/O device, etc. are divided into multiple logical partitions in which operating systems are run independently. In a computing system provided with logical partitions, a basic program called a hypervisor for controlling logical partitions is usually run. A hypervisor assigns computing resources to the logical partitions so that each logical partition operates as a single virtual computer.
The technology for logical partitioning is used for purposes including implementing a multi-operating system in which multiple different operating systems are run in a single computer and running applications in parallel by viewing a single computer as virtual parallel computers.
Home users usually subscribe to a single line and so only one global IP address for connection to an external network is available. This poses a challenge if it is desired that the logical partitions in a multi-partition system concurrently communicate with an external entity. In such a case, some mechanism is needed which allows a single IP address to be shared by multiple logical partitions. To allow multiple computers in a local network to communicate with an external entity, a router is normally installed at a point of connection to an external network. The router converts between global IP addresses and private IP addresses by running network address translation (NAT).
The header of a TCP or a UDP packet contains a checksum including source and destination IP addresses and source and destination port numbers. NAT requires updating of a checksum when changing the IP address or the port number of a packet. Thus, significant overhead is incurred.